Semiconductor package

ABSTRACT

A semiconductor package including a package substrate, a connection substrate on the package substrate and having on a lower corner of the connection substrate a recession that faces a top surface of the package substrate, a semiconductor chip on the connection substrate, a plurality of first connection terminals connecting the connection substrate to the semiconductor chip, and a plurality of second connection terminals connecting the package substrate to the connection substrate. The recession is laterally spaced apart from the second connection terminals.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. nonprovisional application claims priority under 35 U.S.C §119 to Korean Patent Application No. 10-2020-0086641 filed on Jul. 14,2020 in the Korean Intellectual Property Office, the disclosure of whichis hereby incorporated by reference in its entirety.

BACKGROUND

The present inventive concepts relate to a semiconductor package and/ora method of fabricating the same, and more particularly, to asemiconductor package with increased reliability.

Portable devices have been increasingly demanded in recent electronicproduct markets, where much portability may be achieved through areduction in size and weight of electronic parts mounted on the portabledevices. To accomplish the reduction in size and weight of theelectronic parts, there is a desire for technology not only to reduceeach size of mounting parts, but to integrate a number of individualdevices on a single package using, for example, a chip-on-wafer (CoW)multi-chip packaging, in which multiple dies are incorporatedside-by-side on a silicon interposer to achieve better interconnectdensity. However, in fabricating such CoW structures, the interposer mayexperience stresses that lead to cracks on, for example, an under-filllayer.

SUMMARY

Some example embodiments of the present inventive concepts provide asemiconductor package with increased reliability.

An object of the present inventive concepts is not limited to thementioned above, and other objects which have not been mentioned abovewill be clearly understood to those skilled in the art from thefollowing description.

According to some example embodiments of the present inventive concepts,a semiconductor package may include: a package substrate; a connectionsubstrate on the package substrate, the connection substrate having arecession on a lower corner of the connection substrate, the recessionfacing a top surface of the package substrate; a semiconductor chip onthe connection substrate; and a plurality of connection terminalsconnecting the package substrate to the connection substrate such thatthe recession is laterally spaced apart from the plurality of connectionterminals.

According to some example embodiments of the present inventive concepts,a semiconductor package may include: a package substrate; a connectionsubstrate on the package substrate, the connection substrate including abase substrate, a plurality of upper pads on a top surface of the basesubstrate, a plurality of lower pads on a bottom surface of the basesubstrate, and a plurality of through vias penetrating the basesubstrate and connecting the upper pads to the lower pads, theconnection substrate including a recession on a lower corner thereofsuch that a width of the recession is greater than a distance between asidewall of the connection substrate and an outermost one of the upperpads; a chip stack on the connection substrate, the chip stack includinga plurality of first semiconductor chips that are vertically stacked; asecond semiconductor chip spaced apart from the chip stack on theconnection substrate; a plurality of first connection terminalsconnecting the connection substrate to the chip stack and connecting theconnection substrate to the second semiconductor chip; a firstunder-fill layer filling a gap between the chip stack and the connectionsubstrate and a gap between the second semiconductor chip and theconnection substrate; a molding layer on the connection substrate, themolding layer covering the chip stack and the second semiconductor chip;a plurality of second connection terminals connecting the packagesubstrate to the connection substrate; a second under-fill layer fillinga gap between the package substrate and the connection substrate; and aheat radiation structure on the package substrate, the heat radiationstructure covering the connection substrate, the chip stack, and thesecond semiconductor chip.

Details of other example embodiments are included in the description anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a simplified plan view showing a semiconductorpackage according to some example embodiments of the present inventiveconcepts.

FIG. 2 illustrates a cross-sectional view taken along line I-I′ of FIG.1 , showing a semiconductor package according to some exampleembodiments of the present inventive concepts.

FIGS. 3, 4, 5, and 6 illustrate enlarged views showing section P of FIG.2 .

FIGS. 7 to 12 illustrate cross-sectional views showing a method offabricating a semiconductor package according to some exampleembodiments of the present inventive concepts.

DETAILED DESCRIPTION

The following will now describe a semiconductor package and a method offabricating the same according to some example embodiments of thepresent inventive concepts in conjunction with the accompanyingdrawings.

FIG. 1 illustrates a simplified plan view showing a semiconductorpackage according to some example embodiments of the present inventiveconcepts. FIG. 2 illustrates a cross-sectional view taken along lineI-I′ of FIG. 1 , showing a semiconductor package according to someexample embodiments of the present inventive concepts. FIGS. 3, 4, 5,and 6 illustrate enlarged views showing section P of FIG. 2 .

Referring to FIGS. 1 and 2 , a semiconductor package may include a firstsemiconductor chip 100, second semiconductor chips 200, a connectionsubstrate 110, a package substrate 500, and a heat radiation structure600.

The first and second semiconductor chips 100 and 200 may be disposed ona top surface of the connection substrate 110. The first and secondsemiconductor chips 100 and 200 may be connected through firstconnection terminals 50 to the connection substrate 110.

The first semiconductor chip 100 may have chip pads 11 on a bottomsurface thereof, and each of the second semiconductor chips 200 mayinclude chip pads 21 on a bottom surface thereof. The first connectionterminals 50 may be attached to the chip pads 11 and 21 of the first andsecond semiconductor chips 100 and 200. The first connection terminals50 may be one or more of solder balls, conductive bumps, and conductivepillars. The first connection terminals 50 may include one or more ofcopper, tin, and lead. The first connection terminals 50 may have theirthickness of, for example, about 30 μm to about 70 μm.

The first semiconductor chip 100 may be a logic chip including aprocessor, such as a microelectromechanical system (MEMS) device, anoptoelectronic device, a central processing unit (CPU), a graphicprocessing unit (GPU), a mobile application, or a digital signalprocessor (DSP). The first semiconductor chip 100 may have a thicknessranging from about 700 μm to about 775 μm.

The second semiconductor chips 200 may be spaced apart from the firstsemiconductor chip 100 and disposed on the connection substrate 110.Each of the second semiconductor chips 200 may include a plurality ofmemory chips 20 that are vertically stacked. The plurality of memorychips 20 may be electrically connected to each other through the chippads 21, chip through vias 25, and connection bumps 35. The memory chips20 may be stacked on the connection substrate 110 so as to allow theirsidewalls to align with each other. An adhesive layer 30 may be providedbetween the memory chips 20. The adhesive layer 30 may be, for example,a polymer tape including a dielectric material. The adhesive layer 30may be interposed between the connection bumps 35, and thus anelectrical short may be inhibited (or, alternatively, prevented) betweenthe connection bumps 35.

The connection substrate 110 may be provided thereon with a moldinglayer 120 that covers the first and second semiconductor chips 100 and200. The molding layer 120 may have a sidewall aligned with that of theconnection substrate 110. The molding layer 120 may have a top surfacesubstantially coplanar with those of the first and second semiconductorchips 100 and 200. The molding layer 120 may include a dielectricpolymer, such as an epoxy molding compound (EMC).

A first under-fill layer 160 may be interposed between the firstsemiconductor chip 100 and the connection substrate 110 and between thesecond semiconductor chips 200 and the connection substrate 110. Thefirst under-fill layer 160 may fill gaps between the first connectionterminals 50. The first under-fill layer 160 may include, for example, athermo-curable resin or a photo-curable resin. The first under-filllayer 160 may further include an inorganic filler or an organic filler.In some example embodiments, the first under-fill layer 160 may beomitted, and instead the molding layer 120 may fill gaps between theconnection substrate 110 and the bottom surfaces of the first and secondsemiconductor chips 100 and 200.

The connection substrate 110 may be disposed on the package substrate500 and connected through second connection terminals 150 to the packagesubstrate 500. The connection substrate 110 may include a chip regionand an edge region around the chip region. The first and secondsemiconductor chips 100 and 200 may be disposed on the chip region ofthe connection substrate 110.

For example, referring to FIGS. 2 and 3 , the connection substrate 110may include a base substrate 111, through vias 113, a redistributionlayer including connection lines 117, and lower and upper pads 115 and119, respectively.

The base substrate 111 may be a silicon substrate or asilicon-on-insulator (SOI) substrate. Alternatively, the base substrate111 may be a glass substrate, a ceramic substrate, a polymer substrate,or any suitable substrate that can provide proper protection and/or aninterconnection function. The base substrate 111 may include activeelectronic devices and/or passive electronic devices. A passivationdielectric layer may be disposed on each of top and bottom surfaces ofthe base substrate 111.

The through vias 113 may penetrate the base substrate 111, and thethrough vias 113 and the connection lines 117 may include a metallicmaterial, such as tungsten (W), aluminum (Al), or copper (Cu).

The lower pads 115 may be disposed on a bottom surface 110 a of theconnection substrate 110, and the upper pads 119 may be disposed on atop surface 110 b of the connection substrate 110. The lower pads 115may be electrically connected to the upper pads 119 through theconnection lines 117 and the through vias 113.

The second connection terminals 150 may be attached to the lower pads115 of the connection substrate 110. The second connection terminals 150may be electrically connected to the upper pads 119 through the lowerpads 115, the through vias 113, and the connection lines 117. The secondconnection terminals 150 may be solder balls formed of tin, lead, and/orcopper. The second connection terminals 150 may have their thickness ofabout 40 μm to about 80 μm.

Referring to FIGS. 2 and 3 , the connection substrate 110 may have arecession RS on a lower corner thereof. For example, the recession RSmay be formed on a lower corner of the base substrate 111 and may facethe package substrate 500. The connection substrate 110 may have athickness T1 of about 100 μm to about 110 μm on the chip region thereofand a minimum thickness T2 of about 30 μm to about 50 μm on the sidewallthereof.

The recession RS may be laterally spaced apart from the secondconnection terminals 150. The recession RS may vertically overlap atleast one of the upper pads 119 of the connection substrate 110. Theconnection substrate 110 may have first and second sidewalls that faceeach other, and the recessions RS formed on the first and secondsidewalls may be mirror-symmetrical with each other.

As shown in FIG. 3 , the recession RS may have a rounded surface, andwhen viewed from the bottom surface 110 a of the connection substrate110, a depth of the recession RS may decrease as departing from thesidewall of the connection substrate 110. When viewed from the bottomsurface 110 a of the connection substrate 110, the recession RS may havea maximum depth of about 70 μm to about 90 μm.

The recession RS may have a width A1 greater than a distance al betweenthe sidewall of the connection substrate 110 and an outermost upper pad119 of the connection substrate 110. For example, the width A1 of therecession RS may range from about 100 μm to about 120 μm.

In some example embodiments, referring to FIG. 4 , the recession RS mayhave a stepwise surface. In some example embodiments, referring to FIG.5 , the recession RS may have a discontinuous surface. For example, therecession RS may have a first curved surface and a second curved surfacethat have different radius curvatures from each other. In some exampleembodiments, referring to FIG. 6 , the connection substrate 110 may havea first part with a first thickness and a second part with a secondthickness, and the recession RS of the connection substrate 110 may bedefined by the first part and the second part.

The connection substrate 110 and the package substrate 500 may havetherebetween a second under-fill layer 260 that fills gaps between thesecond connection terminals 150. The second under-fill layer 260 mayfill the recession RS of the connection substrate 110 and may partiallycover the sidewall of the connection substrate 110. The secondunder-fill layer 260 may be in direct contact with a surface of therecession RS. The second under-fill layer 260 may include, for example,a thermo-curable resin or a photo-curable resin. The second under-filllayer 260 may further include an inorganic filler or an organic filler.

The package substrate 500 may be, for example, a printed circuit board,a flexible substrate, or a tape substrate. For example, the packagesubstrate 500 may be one of a flexible printed circuit board, a rigidprinted circuit board, and a combination thereof, each of which boardsincludes internal lines 521 formed therein.

The package substrate 500 may have a top surface and a bottom surfacethat face each other, and may include upper coupling pads 511, externalcoupling pads 513, and internal lines 521. The upper coupling pads 511may be arranged on the top surface of the package substrate 500, and theexternal coupling pads 513 may be arranged on the bottom surface of thepackage substrate 500. The upper coupling pads 511 may be electricallyconnected through the internal lines 521 to the external coupling pads513. External coupling terminals 550 may be attached to the externalcoupling pads 513. A ball grid array (BGA) may be provided as theexternal coupling terminals 550.

The heat radiation structure 600 may include a thermal conductivematerial. The thermal conductive material may include a metallicmaterial (e.g., copper and/or aluminum) or a carbon-containing material(e.g., graphene, graphite, and/or carbon nano-tube). The heat radiationstructure 600 may have relatively high thermal conductivity. Forexample, a single metal layer or a plurality of stacked metal layers maybe used as the heat radiation structure 600. For another example, theheat radiation structure 600 may include a heat sink or a heat pipe. Foranother example, the heat radiation structure 600 may be configured touse water cooling.

A thermal conductive layer 700 may be interposed between thesemiconductor package and the heat radiation structure 600. The thermalconductive layer 700 may be in contact with a top surface of thesemiconductor package and a bottom surface of the heat radiationstructure 600. The thermal conductive layer 700 may include a thermalinterface material (TIM). The thermal interface material may include,for example, a polymer and thermal conductive particles. The thermalconductive particles may be distributed in the polymer. When thesemiconductor package operates, heat produced from the semiconductorpackage may be transferred through the thermal conductive layer 700 tothe heat radiation structure 600.

FIGS. 7 to 12 illustrate cross-sectional views showing a method offabricating a semiconductor package according to some exampleembodiments of the present inventive concepts.

Referring to FIG. 7 , a substrate W may be provided on a carriersubstrate CS. An adhesive layer ADL may be used to attach the substrateW onto the carrier substrate CS.

The substrate W may include chip regions CR and a scribe line region SRthat surrounds each of the chip regions CR. The chip regions CR may betwo-dimensionally arranged along rows and columns.

The substrate W may include a base substrate 111, through vias 113, aredistribution layer including connection lines 117, and lower and upperpads 115 and 119. The lower pads 115 may be formed on a bottom surfaceof the substrate W, and the redistribution layer may be formed on a topsurface of the substrate W. The redistribution layer may include theconnection lines 117 that connect the upper pads 119 to the through vias113. The lower pads 115 may be electrically connected to the upper pads119 through the connection lines 117 and the through vias 113.

The adhesive layer ADL may be provided between the substrate W and thecarrier substrate CS, and may protect the lower pads 115.

Referring to FIG. 8 , a first semiconductor chip 100 and a plurality ofsecond semiconductor chips 200 may be attached onto each chip region CRof the substrate W.

For example, the first semiconductor chip 100 may include chip pads 11on a bottom surface thereof, and each of the second semiconductor chips200 may include chip pads 21 on a bottom surface thereof. The first andsecond semiconductor chips 100 and 200 may be disposed to allow theirchip pads 11 and 21 to face the top surface of the substrate W. The chippads 11 and 21 of the first and second semiconductor chips 100 and 200may be connected through first connection terminals 50 to the upper pads119 of the substrate W.

After the attachment of the first and second semiconductor chips 100 and200, a first under-fill layer 160 may fill gaps between the firstconnection terminals 50 on each of the chip regions CR.

Afterwards, a molding layer 120 may be formed on the substrate W,covering top surfaces of the first and second semiconductor chips 100and 200. The molding layer 120 may be thicker than the first and secondsemiconductor chips 100 and 200, and may fill gaps between the first andsecond semiconductor chips 100 and 200. The molding layer 120 mayinclude a dielectric polymer, such as an epoxy molding compound (EMC).

Referring to FIG. 9 , after the formation of the molding layer 120, athinning process may be performed on the molding layer 120. The thinningprocess may include a grinding process, a chemical mechanical polishingprocess, or an etching process. After the thinning process, a topsurface of the molding layer 120 may be located at substantially thesame level as that of the top surfaces of the first and secondsemiconductor chips 100 and 200.

After the thinning process performed on the molding layer 120, a supporttape TP may be attached to the top surfaces of the molding layer 120 andthe first and second semiconductor chips 100 and 200. In addition, theadhesive layer ADL may be removed from the bottom surface of thesubstrate W.

On the bottom surface of the substrate W, a laser grooving process maybe performed along the scribe line region SR. The laser grooving processmay include forming a recession RS on the bottom surface of thesubstrate W by allowing the scribe line region SR to receive a stealthlaser L that passes through the substrate W. For example, the recessionRS may be formed to have a rounded bottom surface due to the lasergrooving process. The recession RS may have a surface that depends on awidth and/or intensity of a laser beam used in the laser groovingprocess. The stealth laser L may be irradiated in a linear or zigzagfashion along the scribe line region SR. The stealth laser L may have awavelength ranging from about 900 nm to about 1,700 nm, but the presentinventive concepts are not limited thereto.

It is described by way of example that the laser grooving process isperformed to form the recession RS, but the present inventive conceptsare not limited thereto and the recession RS may be formed by a bladesawing process, a wet etching process, or a dry etching process.

The recession RS may be formed on the scribe line region SR and an edgeof the chip region CR. The recession RS may be laterally spaced apartfrom the lower pads 115 on the bottom surface of the substrate W. Therecession RS may vertically overlap at least one of the upper pads 119formed on the top surface of the substrate W.

The recession RS may have a width W1 greater than that of the scribeline region SR. For example, the width W1 of the recession RS may rangefrom about 220 μm to about 240 μm. The recession RS may have a depththat decreases as departing from the scribe line region SR. For example,the depth of the recession RS may range from about 70 μm to about 90 μm.

Referring to FIG. 10 , second connection terminals 150 may be attachedto the lower pads 115 of the substrate W, and the second connectionterminals 150 may be electrically connected to the upper pads 119through the connection lines 117 and the through vias 113. The secondconnection terminals 150 may be solder balls formed of tin, lead, and/orcopper.

Referring to FIG. 11 , the substrate W may be provided on its bottomsurface with an adhesive mold layer 130 that covers the secondconnection terminals 150, and a sawing tape TP may be attached onto theadhesive mold layer 130.

A sawing process may be performed along the scribe line region SR,thereby separating the chip regions CR from each other. The sawingprocess may include using a blade BL or laser to cut the substrate W.The chip regions CR of the substrate W may be separated into a pluralityof semiconductor chips on the sawing tape TP. During the sawing process,a cutting width W2 may be less than the width W1 of the recession RS.For example, the cutting width W2 of the sawing process may range fromabout 30 μm to about 40 μm.

It is illustrated by way of example that the sawing tape TP is attachedonto the adhesive mold layer 130, and that the sawing process startsfrom the molding layer 120, but the present inventive concepts are notlimited thereto and the sawing process may be performed starting fromthe adhesive mold layer 130.

Referring to FIG. 12 , the separated semiconductor chip may be attachedonto a package substrate 500.

The package substrate 500 may have a top surface and a bottom surfacethat face each other, and may include upper coupling pads 511, externalcoupling pads 513, and internal lines 521.

The second connection terminals 150 may be attached between the uppercoupling pads 511 of the package substrate 500 and the lower pads 115 ofthe connection substrate 110. External coupling terminals 550 may beattached to the external coupling pads 513. A ball grid array (BGA) maybe provided as the external coupling terminals 550.

After the attachment of the semiconductor chip, a second under-filllayer 260 may fill gaps between the connection substrate 110 and thepackage substrate 500. According to some example embodiments, becausethe connection substrate 110 has the recession RS on a lower cornerthereof, when the second under-fill layer 260 is formed, the secondunder-fill layer 260 may be inhibited (or, alternatively, prevented)from being cracked due to stress concentrated on the lower corner of theconnection substrate 110.

In addition, because the recession RS is formed on the lower corner ofthe connection substrate 110, a volume of the second under-fill layer260 may become increased below the connection substrate 110 such thatthe second under-fill layer 260 may be reduced or prevented fromprotruding outwardly from a sidewall of the connection substrate 110.

Referring to FIG. 2 , after the formation of the second under-fill layer260, a thermal conductive layer 700 and a heat radiation structure 600may be formed.

According to some example embodiments of the present inventive concepts,because a connection substrate has a recession on a lower cornerthereof, an under-fill layer may be inhibited (or, alternatively,prevented) from being cracked due to stress concentrated on the lowercorner of the connection substrate.

Moreover, because the recession is formed on the lower corner of theconnection substrate, a volume of the under-fill layer is increasedbelow the connection substrate such that the under-fill layer may bereduced or prevented from protruding outwardly from a sidewall of theconnection substrate.

Although the present inventive concepts have been described inconnection with some example embodiments of the present inventiveconcepts illustrated in the accompanying drawings, it will be understoodto those skilled in the art that various changes and modifications maybe made without departing from the technical spirit and essentialfeature of the present inventive concepts. It will be apparent to thoseskilled in the art that various substitution, modifications, and changesmay be thereto without departing from the scope and spirit of thepresent inventive concepts.

What is claimed is:
 1. A semiconductor package, comprising: a packagesubstrate; a connection substrate on the package substrate, theconnection substrate including a top surface, a bottom surface and apair of side walls extending between the top surface and the bottomsurface, the connection substrate having a recession on a lower cornerof at least one of the pair of side walls, the recession facing a topsurface of the package substrate; a semiconductor chip on the connectionsubstrate; and a plurality of connection terminals connecting thepackage substrate to the connection substrate such that the recession islaterally spaced apart from the plurality of connection terminals andrelatively closer than the plurality of connection terminals to the atleast one of the pair of side walls.
 2. The semiconductor package ofclaim 1, wherein the connection substrate includes a plurality of upperpads on a top surface of the connection substrate and a plurality oflower pads on a bottom surface of the connection substrate, the upperpads connected to the semiconductor chip, and the lower pads connectedto the package substrate, and a width of the recession is greater than adistance between a sidewall of the connection substrate and an outermostone of the upper pads.
 3. The semiconductor package of claim 2, whereinthe recession vertically overlaps at least one of the upper pads.
 4. Thesemiconductor package of claim 1, wherein a width of the recession is ina range of about 100 μm to about 120 μm.
 5. The semiconductor package ofclaim 1, wherein the connection substrate includes a chip region and anedge region around the chip region, a sidewall of the connectionsubstrate having a first thickness, and the chip region of theconnection substrate having a second thickness, the second thicknessbeing greater than the first thickness.
 6. The semiconductor package ofclaim 1, wherein a depth of the recession from a bottom surface of theconnection substrate gradually decreases towards the semiconductor chipfrom a sidewall of the connection substrate.
 7. The semiconductorpackage of claim 1, wherein a maximum depth of the recession is in arange of about 70 μm to about 90 μm from a bottom surface of theconnection substrate.
 8. The semiconductor package of claim 1, whereinthe recession has a rounded surface.
 9. The semiconductor package ofclaim 1, wherein the recession has a stepwise surface.
 10. Thesemiconductor package of claim 1, further comprising: a plurality offirst connection terminals connecting the connection substrate to thesemiconductor chip; a first under-fill layer filling a gap between thefirst connection terminals between the semiconductor chip and theconnection substrate; and a second under-fill layer filling a gapbetween the connection substrate and the package substrate, therecession being in contact with the second under-fill layer.
 11. Thesemiconductor package of claim 1, further comprising: a molding layer onthe connection substrate and covering the semiconductor chip, themolding layer having a sidewall aligned with a sidewall of theconnection substrate.
 12. A semiconductor package, comprising: a packagesubstrate; a connection substrate on the package substrate, theconnection substrate having a recession on a lower corner of theconnection substrate, the recession facing a top surface of the packagesubstrate; a semiconductor chip on the connection substrate; and aplurality of connection terminals connecting the package substrate tothe connection substrate such that the recession is laterally spacedapart from the plurality of connection terminals, wherein the connectionsubstrate includes a chip region and an edge region that surrounds thechip region, the semiconductor chip being on the chip region with therecession defined along the edge region.
 13. The semiconductor packageof claim 1, wherein the connection substrate has a first sidewall and asecond sidewall that face each other, the recession includes a firstrecession adjacent to the first sidewall and a second recession adjacentto the second sidewall, the second recession being mirror-symmetricalwith the first recession.
 14. A semiconductor package, comprising: apackage substrate; a connection substrate on the package substrate, theconnection substrate including a base substrate, a plurality of upperpads on a top surface of the base substrate, a plurality of lower padson a bottom surface of the base substrate, and a plurality of throughvias penetrating the base substrate and connecting the upper pads to thelower pads, the connection substrate including a recession on a lowercorner thereof such that a width of the recession is greater than adistance between a sidewall of the connection substrate and an outermostone of the upper pads; a chip stack on the connection substrate, thechip stack including a plurality of first semiconductor chips that arevertically stacked; a second semiconductor chip spaced apart from thechip stack on the connection substrate; a plurality of first connectionterminals connecting the connection substrate to the chip stack andconnecting the connection substrate to the second semiconductor chip; afirst under-fill layer filling a gap between the chip stack and theconnection substrate and a gap between the second semiconductor chip andthe connection substrate; a molding layer on the connection substrate,the molding layer covering the chip stack and the second semiconductorchip; a plurality of second connection terminals connecting the packagesubstrate to the connection substrate; a second under-fill layer fillinga gap between the package substrate and the connection substrate; and aheat radiation structure on the package substrate, the heat radiationstructure covering the connection substrate, the chip stack, and thesecond semiconductor chip.
 15. The semiconductor package of claim 14,wherein the recession vertically overlaps at least one of the upperpads.
 16. The semiconductor package of claim 14, wherein a depth of therecession from a bottom surface of the connection substrate decreasesfrom the sidewall of the connection substrate.
 17. The semiconductorpackage of claim 14, wherein the recession has a rounded surface incontact with the second under-fill layer.
 18. The semiconductor packageof claim 14, wherein a sidewall of the molding layer is aligned with thesidewall of the connection substrate.
 19. The semiconductor package ofclaim 14, wherein a top surface of the molding layer, a top surface ofthe chip stack, and a top surface of the second semiconductor chip areat substantially a same level.
 20. The semiconductor package of claim14, wherein the width of the recession is between 100 μm to 120 μm, anda maximum depth of the recession from a bottom surface of the connectionsubstrate is between 70 μm to 90 μm.